Methods for making cured sealants by actinic radiation and related compositions

ABSTRACT

Disclosed are methods for making a cured sealant. The methods include depositing an uncured sealant composition on a substrate and exposing the uncured sealant composition to actinic radiation to provide a cured sealant. The uncured sealant composition includes a thiol-terminated polythioether, a polyene comprising a polyvinyl ether and/or a polyallyl compound, and a hydroxy-functional vinyl ether. Related sealant compositions are also disclosed.

This application is a continuation of U.S. application Ser. No.14/560,565, filed on Dec. 4, 2014, which is a continuation-in-part ofU.S. application Ser. No. 13/659,074, filed on Oct. 24, 2012, now issuedU.S. Pat. No. 9,533,798, which is a continuation-in-part of U.S.application Ser. No. 12/855,729, filed on Aug. 13, 2010, now issued U.S.Pat. No. 8,932,685, and U.S. application Ser. No. 13/659,074 is acontinuation-in-part of U.S. application Ser. No. 12/855,725, filed onAug. 13, 2010, now issued U.S. Pat. No. 8,729,198, each of which isincorporated by reference in its entirety.

CROSS-REFERENCE TO RELATED APPLICATION

This application is related to U.S. Application Publication No.2012/0040103, U.S. Application Publication No. 2013/0284359, and U.S.Application Publication No. 2014/0186543.

FIELD OF THE INVENTION

The present invention is directed to methods for making a cured sealant,such as an aerospace sealant, through the use of actinic radiation. Thepresent invention is also directed to compositions suitable for use insuch methods.

BACKGROUND OF THE INVENTION

Thiol-terminated sulfur-containing compounds are known to be well-suitedfor use in various applications, such as aerospace sealant compositions,due, in large part, to their fuel-resistant nature upon cross-linking.Other desirable properties for aerospace sealant compositions includelow temperature flexibility, short curing time (the time required toreach a predetermined strength) and elevated-temperature resistance,among others. Sealant compositions exhibiting at least some of thesecharacteristics and containing thiol-terminated sulfur-containingcompounds are described in, for example, U.S. Pat. Nos. 2,466,963,4,366,307, 4,609,762, 5,225,472, 5,912,319, 5,959,071, 6,172,179,6,232,401, 6,372,849 and 6,509,418.

Thus, sealant compositions that are storage stable but, when applied toa substrate, can be cured quickly to form a cured sealant having thecharacteristics described above are desired. The present invention wasmade in view of the foregoing.

SUMMARY OF THE INVENTION

In certain respects, the present invention is directed to methods formaking a cured sealant comprising: (a) depositing an uncured sealantcomposition on a substrate; and (b) exposing the uncured sealantcomposition to actinic radiation to provide a cured sealant. In thesemethods, the uncured sealant composition comprises: (i) athiol-terminated polythioether; and (ii) a polyene comprising apolyvinyl ether and/or a polyallyl compound.

In other respects, the present invention is directed to compositionscomprising: (a) a thiol-terminated polythioether; and (b) a polyenecomprising a polyvinyl ether and/or a polyallyl compound. In thesecompositions, an essentially stoichiometric equivalent amount of thiolgroups to ene groups is present.

In still other respects, the present invention is directed tocompositions comprising: (a) a thiol-terminated polythioether; (b) apolyene comprising a polyvinyl ether and/or a polyallyl compound; and(c) a photoinitiator.

In another aspect, unreacted compositions are provided comprising: (a) athiol-terminated polythioether; (b) a polyene comprising a polyvinylether compound; (c) a hydroxy-functional vinyl ether; and (d) asulfur-containing ethylenically unsaturated silane adduct, wherein thesulfur-containing ethylenically unsaturated silane adduct comprises thereaction product of reactants comprising (i) a mercaptosilane, and (ii)a polyene.

In another aspect, cured sealants prepared by curing compositionsprovided by the present disclosure are provided.

In another aspect, methods for making a cured sealant are disclosedcomprising: (a) depositing the composition of claim 17 on a substrate;and (b) exposing the unreacted sealant composition to actinic radiationto provide a cured sealant.

The present invention is also directed to, inter alia, sealantsdeposited from such methods and compositions.

DETAILED DESCRIPTION OF THE INVENTION

For purposes of the following detailed description, it is to beunderstood that the invention may assume various alternative variationsand step sequences, except where expressly specified to the contrary.Moreover, other than in any operating examples, or where otherwiseindicated, all numbers expressing, for example, quantities ofingredients used in the specification and claims are to be understood asbeing modified in all instances by the term “about”. Accordingly, unlessindicated to the contrary, the numerical parameters set forth in thefollowing specification and attached claims are approximations that mayvary depending upon the desired properties to be obtained by the presentinvention. At the very least, and not as an attempt to limit theapplication of the doctrine of equivalents to the scope of the claims,each numerical parameter should at least be construed in light of thenumber of reported significant digits and by applying ordinary roundingtechniques.

Notwithstanding that the numerical ranges and parameters setting forththe broad scope of the invention are approximations, numerical valuesset forth in the specific examples are reported as precisely aspossible. Any numerical value, however, inherently contains certainerrors necessarily resulting from the standard variation found in theirrespective testing measurements.

Also, it should be understood that any numerical range recited herein isintended to include all sub-ranges subsumed therein. For example, arange of “1 to 10” is intended to include all sub-ranges between (andincluding) the recited minimum value of 1 and the recited maximum valueof 10, that is, having a minimum value equal to or greater than 1 and amaximum value of equal to or less than 10.

As indicated, certain embodiments of the present invention are directedto methods for making a cured sealant. These methods comprise depositingan uncured sealant composition on a substrate. The uncured sealantcomposition can be deposited on any of a variety of substrates. Commonsubstrates can include titanium, stainless steel, aluminum, anodized,primed, organic coated and chromate coated forms thereof, epoxy,urethane, graphite, fiberglass composite, Kevlar®, acrylics andpolycarbonates. The uncured sealant composition can be deposited on thesurface of a substrate or over an underlayer, such as a primer layer ora previously applied sealant.

The uncured sealant compositions used in the methods of the presentinvention comprise a thiol-terminated polythioether. As used herein, theterm “polythioether” refers to compounds comprising at least twothioether linkages, that is “—C—S—C—” linkages. Thiol-terminatedpolythioethers and methods for their production, which are suitable foruse in the present invention include, for example, those disclosed inU.S. Pat. No. 4,366,307 at col. 3, line 7 to col. 9, line 51 and U.S.Pat. No. 6,172,179 at col. 5, line 42 to col. 12, line 7, the citedportions of which being incorporated by reference herein. In certainembodiments, therefore, the thiol-terminated polythioether comprises apolythioether that includes a structure having the formula (I):

—R¹—[—S—(CH₂)₂—O—[—R²—O—]_(m)—(CH₂)₂—S—R¹—]_(n)—  (I)

wherein: (1) each R¹ independently denotes a C₂₋₆ n-alkylene, C₂₋₆branched alkylene, C₆₋₈ cycloalkylene or C₆₋₁₀ alkylcycloalkylene group,—[(—CH₂—)_(p)—X—]_(q)—(—CH₂—)_(r)—, or—[(—CH₂—)_(p)—X—]_(q)—(—CH₂—)_(r)— in which at least one —CH₂— unit issubstituted with a methyl group, wherein (i) each X is independentlyselected from O, S and —NR⁶—, wherein R⁶ denotes H or methyl; (ii) p isan integer having a value ranging from 2 to 6; (iii) q is an integerhaving a value ranging from 0 to 5; and (iv) r is an integer having avalue ranging from 2 to 10; (2) each R² independently denotes a C₂₋₆n-alkylene, C₂₋₆ branched alkylene, C₆₋₈ cycloalkylene or C₆₋₁₀alkylcycloalkylene group, or —[(—CH₂—)_(p)—X—]_(q)—(—CH₂—)_(r)—, wherein(i) each X is independently selected from O, S and —NR⁶—, wherein R⁶denotes H or methyl; (ii) p is an integer having a value ranging from 2to 6; (iii) q is an integer having a value ranging from 0 to 5; and (iv)r is an integer having a value ranging from 2 to 10; (3) m is a rationalnumber from 0 to 10; and (4) n is an integer having a value ranging from1 to 60. Such polythioethers and methods for their production aredescribed in U.S. Pat. No. 6,172,179 within the portion thereofincorporated herein by reference above.

More particularly, in certain embodiments, the thiol-terminatedpolythioether has a structure according to formula (II):

HS—R¹—[—S—(CH₂)₂—O—[—R²—O—]_(m)—(CH₂)₂—S—R¹—]_(n)—SH   (II)

in which R¹, R², m and n are as described above with respect to formula(I).

In certain embodiments, the thiol-terminated polythioether ispolyfunctionalized. As a result, in certain embodiments, thethiol-terminated polythioether has a structure according to formula(III):

B-(A-[R³]_(y)—SH)_(z)  (III)

wherein: (1) A denotes a structure according to formula (I); (2) y is 0or 1; (3) R³ denotes a single bond when y=0 and—S—(CH₂)₂—[—O—R²—]_(m)—O— when y=1; (4) z is an integer from 3 to 6; and(5) B denotes a z-valent residue of a polyfunctionalizing agent.

Suitable methods for making such polyfunctionalized polythioetherpolymers are disclosed in, for example, U.S. Pat. No. 6,172,179 at col.7, line 48 to col. 12, line 7, the cited portion of which beingincorporated herein by reference above.

The uncured sealant compositions used in the methods of the presentinvention also comprise a polyene comprising a polyvinyl ether and/or apolyallyl compound. As used herein, the term “polyene” refers to acompound containing at least two carbon-carbon double bonds (C═C).

In certain embodiments, the polyallyl compound present in the uncuredsealant composition comprises a triallyl compound, which refers tocompounds comprising three allyl groups (C═C—C) and which include, forexample, triallyl cyanurate (TAC) and triallyl isocyanurate (TAIC).

In certain embodiments, the polyene comprises a polyvinyl ether.Suitable polyvinyl ethers include, for example, those represented byFormula (IV):

CH₂—CH—O—(R⁵—O—)_(m)—CH═CH₂  (IV)

where R⁵ in formula (IV) is a C₂₋₆ n-alkylene group, a C₂₋₆ branchedalkylene group, a C₆₋₈ cycloalkylene group, a C₆₋₁₀ alkylcycloalkylenegroup, or—[(—CH₂—)_(p)—O—]_(q)—(—CH₂—)_(r)—, where p is an integer having a valueranging from 2 to 6, q is an integer having a value ranging from 1 to 5,and r is an integer having a value ranging from 2 to 10.

The materials of formula (IV) are divinyl ethers. Suitable divinylethers include those compounds having at least one oxyalkylene group,such as from 1 to 4 oxyalkylene groups, i.e., those compounds in which min formula (IV) is an integer from 1 to 4. In some cases, m in formula(IV) is an integer from 2 to 4. It is also possible to employcommercially available divinyl ether mixtures to produce the polymers ofthe present invention. Such mixtures are characterized by a non-integralaverage value for the number of oxyalkylene units per molecule. Thus, min formula (IV) can also take on rational number values between 0 and10.0, such as between 1.0 and 10.0, between 1.0 and 4.0, or between 2.0and 4.0.

Suitable divinyl ether monomers for use in the present inventioninclude, for example, divinyl ether, ethylene glycol divinyl ether(EG-DVE) (R in formula (IV) is ethylene and m is 1), butanediol divinylether (BD-DVE) (R in formula (IV) is butylene and m is 1), hexanedioldivinyl ether (HD-DVE) (R in formula (IV) is hexylene and m is 1),diethylene glycol divinyl ether (DEG-DVE) (R in formula (IV) is ethyleneand m is 2), triethylene glycol divinyl ether (R in formula (IV) isethylene and m is 3), tetraethylene glycol divinyl ether (R in formula(IV) is ethylene and m is 4), cyclohexanedimethanol divinyl ether,polytetrahydrofuryl divinyl ether and mixtures thereof. In some cases,trivinyl ether monomers, such as trimethylolpropane trivinyl ether;tetrafunctional ether monomers, such as pentaerythritol tetravinylether; and mixtures of two or more such polyvinyl ether monomers can beused. The polyvinyl ether material can have one or more pendant groupsselected from alkyl groups, hydroxyl groups, alkoxy groups and aminegroups.

Useful divinyl ethers in which R in formula (IV) is C₂₋₆ branchedalkylene can be prepared by reacting a polyhydroxy compound withacetylene. Exemplary compounds of this type include compounds in which Rin formula (IV) is an alkyl-substituted methylene group such as—CH(CH₃)— (for example “PLURIOL®” blends such as PLURIOL®E-200 divinylether (BASF Corp. of Parsippany, N.J.), for which R in formula (IV) isethylene and m is 3.8) or an alkyl-substituted ethylene (for example—CH₂CH(CH₃)— such as “DPE” polymeric blends including DPE-2 and DPE-3(International Specialty Products of Wayne, N.J.)).

Other useful divinyl ethers include compounds in which R in formula (IV)is polytetrahydrofuryl (poly-THF) or polyoxyalkylene, such as thosehaving an average of about 3 monomer units.

Two or more divinyl ether monomers of the formula (IV) can be used ifdesired.

In certain embodiments, the uncured sealant composition used in themethods of the present invention also comprises an ethylenicallyunsaturated silane, such as, for example, a sulfur-containingethylenically unsaturated silane, which has been shown to, in at leastsome cases, improve the adhesion of a cured sealant formed by themethods of the present invention to a metal substrate (to an extentgreater than achieved when a conventional adhesion promoter, such asthose described below, is used). As used herein, the term“sulfur-containing ethylenically unsaturated silane” refers to amolecular compound that comprises, within the molecule, (i) at least onesulfur (S) atom, (ii) at least one, in some cases at least two,ethylenically unsaturated carbon-carbon bonds, such as a carbon-carbondouble bonds (C═C); and (iii) at least one silane group

wherein R and R₁ each independently represent an organic group and x is1, 2, or 3).

In certain embodiments, the sulfur-containing ethylenically unsaturatedsilane, which is suitable for use in the uncured sealant compositionsused in the methods of the present invention, itself comprises thereaction product of reactants comprising: (i) a mercaptosilane, and (ii)a polyene. As used herein, the term “mercaptosilane” refers to amolecular compound that comprises, within the molecule, (i) at least onemercapto (—SH) group, and (ii) at least one silane group (definedabove). Suitable mercaptosilanes include, for example, those having astructure according to formula (V):

HS—R—Si(R₁)_(m)(OR′)_((3-m))  (V)

wherein: (i) R is a divalent organic group; (ii) R′ is hydrogen or analkyl group; (iii) R₁ is hydrogen or an alkyl group; and (iv) m is aninteger from 0 to 2.

Specific examples of mercaptosilanes, which are suitable for use inpreparing the sulfur-containing ethylenically unsaturated silanessuitable for use in the present invention, include, without limitation,γ-mercaptopropyltrimethoxysilane, γ-mercaptopropyltriethoxysilane,γ-mercaptopropylmethyldimethoxysilane,γ-mercaptopropylmethyldiethoxysilane, mercaptomethyltrimethoxysilanemercaptomethyltriethoxysilane, and the like, including combinationsthereof.

In certain embodiments, the polyene used to prepare thesulfur-containing ethylenically unsaturated silanes suitable for use inthe present invention comprises a triene, which refers to a compoundcontaining three carbon-carbon double bonds, such as is the case withthe triallyl compounds mentioned above.

The Examples herein illustrate a suitable method for producing thesulfur-containing ethylenically unsaturated silanes suitable for use inthe present invention. In certain embodiments, the polyene comprises atriene, such as one or more of the foregoing triallyl compounds, and themercaptosilane and triene are reacted together in relative amounts suchthat the resulting reaction product theoretically comprises an averageof at least two ethylenically unsaturated groups per molecule.

The compositions of the present invention will often contain anessentially stoichiometric equivalent amount of thiol groups to “ene”groups in order to obtain a cured sealant having acceptable sealantproperties as described herein upon exposure of the composition toactinic radiation. As used herein, “essentially stoichiometricequivalent” means that the number of thiol groups and “ene” groupspresent in the compositions differ by no more than 10% from each other,in some cases, no more than 5% or, in some cases, no more than 1% or nomore than 0.1%. In some cases, the number of thiol groups and “ene”groups present in the composition are equal. Moreover, as will beappreciated, the source of “ene” groups in the compositions of thepresent invention can include the ethylenically unsaturated silaneitself (if used) as well as the other polyene(s) included in thecomposition. In certain embodiments, the ethylenically unsaturatedsilane described earlier is present in an amount such that 0.1 to 30,such as 1 to 30, or, in some cases, 10 to 25 percent of the total numberof ethylenically unsaturated groups present in the composition are partof an ethylenically unsaturated silane molecule, based on the number ofethylenically unsaturated groups in the composition.

As indicated, the methods of the present invention comprise exposing theuncured sealant composition to actinic radiation to provide a curedsealant. In certain embodiments, particularly when the cured sealant isto be formed by exposure of the previously described uncured sealantcomposition to UV radiation, the composition also comprises aphotoinitiator. As will be appreciated by those skilled in the art, aphotoinitiator absorbs ultraviolet radiation and transforms it into aradical that initiates polymerization. Photoinitiators are classified intwo major groups based upon a mode of action, either or both of whichmay be used in the compositions described herein. Cleavage-typephotoinitiators include acetophenones, α-aminoalkylphenones, benzoinethers, benzoyl oximes, acylphosphine oxides and bisacylphosphine oxidesand mixtures thereof. Abstraction-type photoinitiators includebenzophenone, Michler's ketone, thioxanthone, anthraquinone,camphorquinone, fluorone, ketocoumarin and mixtures thereof.

Specific nonlimiting examples of photoinitiators that may be used in thepresent invention include benzil, benzoin, benzoin methyl ether, benzoinisobutyl ether benzophenol, acetophenone, benzophenone,4,4′-dichlorobenzophenone, 4,4′-bis(N,N′-dimethylamino)benzophenone,diethoxyacetophenone, fluorones, e.g., the H-Nu series of initiatorsavailable from Spectra Group Ltd.,2-hydroxy-2-methyl-1-phenylpropan-1-one, 1-hydroxycyclohexyl phenylketone, 2-isopropylthixantone, α-aminoalkylphenone, e.g.,2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-1-butanone,acylphosphine oxides, e.g., 2,6-dimethylbenzoyldlphenyl phosphine oxide,2,4,6-trimethylbenzoyldiphenylphosphine oxide, bis(2,4,6-trimethylbenzoyl)phenyl phosphine oxide,2,6-dichlorobenzoyldiphenylphosphine oxide, and2,6-dimethoxybenzoyldiphenylphosphine oxide, bisacylphosphine oxides,e.g., bis(2,6-dimethyoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide,bis(2,6-dimethylbenzoyl)-2,4,4-trimethylpentylphosphine oxide,bis(2,4,6-trimethylbenzoyl)-2,4,4-trimethylpentylphosphine oxide, andbis(2,6-dichlorobenzoyl)-2,4,4-trimethylpentylphosphine oxide, andmixtures thereof.

In certain embodiments, the compositions described herein comprise 0.01up to 15 percent by weight of photoinitiator or, in some embodiments,0.01 up to 10 percent by weight, or, in yet other embodiments, 0.01 upto 5 percent by weight of photoinitiator based on the total weight ofthe composition.

Fillers useful in the certain embodiments of the compositions describedherein include those commonly used in the art, including conventionalinorganic fillers, such as fumed silica, calcium carbonate (CaCO₃), andcarbon black, as well as lightweight fillers. Fillers that aresubstantially transparent to ultraviolet radiation, such as fumedsilica, may be particularly useful in some embodiments. Suitablelightweight fillers include, for example, those described in U.S. Pat.No. 6,525,168 at col. 4, lines 23-55, the cited portion of which beingincorporated herein by reference and those described in United StatesPatent Application Publication No. US 2010-0041839 A1 at [0016] to[0052], the cited portion of which being incorporated herein byreference.

In some embodiments, the compositions described herein include aphotoactive filler. As used herein, the term “photoactive filler” refersto a filler that comprises a material that is photoexcitable uponexposure to, and absorption of, ultraviolet and/or visible radiation. Aphotoactive material is a material that, when exposed to light havinghigher energy than the energy gap between the conduction band and thevalence band of the crystal, causes excitation of electrons in thevalence band to produce a conduction electron thereby laving a holebehind on the particular valence band. Exemplary, but non-limiting,photoactive fillers suitable for use in certain composition describedherein are metal oxides, such as, for example, zinc oxide, tin oxide,ferric oxide, dibismuth trioxide, tungsten trioxide, titanium dioxide(including the brookite, anatase, and/or rutile crystalline forms oftitanium dioxide), and mixtures thereof.

In certain embodiments, the compositions include 5 to 60 weight percentof the filler or combination of fillers, such as 10 to 50 weightpercent, based on the total weight of the composition, so long as thepresence of such fillers in such amounts does not cause a significantdetrimental affect the performance of the composition.

In addition to the foregoing ingredients, certain compositions of theinvention can optionally include one or more of the following: colorants(including photoactive dyes), thixotropes, conventional adhesionpromoters, retardants, solvents and masking agents, among othercomponents.

As used herein, the term “colorant” means any substance that impartscolor and/or other opacity and/or other visual effect to thecomposition. The colorant can be added to the coating in any suitableform, such as discrete particles, dispersions, solutions and/or flakes.A single colorant or a mixture of two or more colorants can be used inthe coatings of the present invention.

Example colorants include pigments, dyes and tints, such as those usedin the paint industry and/or listed in the Dry Color ManufacturersAssociation (DCMA), as well as special effect compositions. A colorantmay include, for example, a finely divided solid powder that isinsoluble but wettable under the conditions of use. A colorant can beorganic or inorganic and can be agglomerated or non-agglomerated.Colorants can be incorporated into the coatings by use of a grindvehicle, such as an acrylic grind vehicle, the use of which will befamiliar to one skilled in the art.

Example pigments and/or pigment compositions include, but are notlimited to, carbazole dioxazine crude pigment, azo, monoazo, diazo,naphthol AS, salt type (flakes), benzimidazolone, isoindolinone,isoindoline and polycyclic phthalocyanine, quinacridone, perylene,perinone, diketopyrrolo pyrrole, thioindigo, anthraquinone, indanthrone,anthrapyrimidine, flavanthrone, pyranthrone, anthanthrone, dioxazine,triarylcarbonium, quinophthalone pigments, diketo pyrrolo pyrrole red(“DPPBO red”), titanium dioxide, carbon black and mixtures thereof. Theterms “pigment” and “colored filler” can be used interchangeably.

Example dyes include, but are not limited to, those that are solventand/or aqueous based such as phthalo green or blue, iron oxide, bismuthvanadate, anthraquinone, peryleneand quinacridone.

Example tints include, but are not limited to, pigments dispersed inwater-based or water miscible carriers such as AQUA-CHEM 896commercially available from Degussa, Inc., CHARISMA COLORANTS andMAXITONER INDUSTRIAL COLORANTS commercially available from AccurateDispersions division of Eastman Chemical, Inc.

As noted above, the colorant can be in the form of a dispersionincluding, but not limited to, a nanoparticle dispersion. Nanoparticledispersions can include one or more highly dispersed nanoparticlecolorants and/or colorant particles that produce a desired visible colorand/or opacity and/or visual effect. Nanoparticle dispersions caninclude colorants such as pigments or dyes having a particle size ofless than 150 nm, such as less than 70 nm, or less than 30 nm.Nanoparticles can be produced by milling stock organic or inorganicpigments with grinding media having a particle size of less than 0.5 mmExample nanoparticle dispersions and methods for making them areidentified in U.S. Pat. No. 6,875,800 B2, which is incorporated hereinby reference. Nanoparticle dispersions can also be produced bycrystallization, precipitation, gas phase condensation, and chemicalattrition (i.e., partial dissolution). In order to minimizere-agglomeration of nanoparticles within the coating, a dispersion ofresin-coated nanoparticles can be used. As used herein, a “dispersion ofresin-coated nanoparticles” refers to a continuous phase in which isdispersed discreet “composite microparticles” that comprise ananoparticle and a resin coating on the nanoparticle. Exampledispersions of resin-coated nanoparticles and methods for making themare identified in U.S. Application Publication No. 2005/0287348 A1 andU.S. Application Publication No. 2006/0251896 A1, each of which isincorporated by reference in its entirety.

Example special effect compositions that may be used in the compositionsof the present invention include pigments and/or compositions thatproduce one or more appearance effects such as reflectance,pearlescence, metallic sheen, phosphorescence, fluorescence,photochromism, photosensitivity, thermochromism, goniochromism and/orcolor-change. Additional special effect compositions can provide otherperceptible properties, such as opacity or texture. In a non-limitingembodiment, special effect compositions can produce a color shift, suchthat the color of the coating changes when the coating is viewed atdifferent angles. Example color effect compositions are identified inU.S. Pat. No. 6,894,086, incorporated herein by reference. Additionalcolor effect compositions can include transparent coated mica and/orsynthetic mica, coated silica, coated alumina, a transparent liquidcrystal pigment, a liquid crystal coating, and/or any compositionwherein interference results from a refractive index differential withinthe material and not because of the refractive index differentialbetween the surface of the material and the air.

In general, the colorant can be present in any amount sufficient toimpart the desired visual and/or color effect. The colorant may comprisefrom 1 to 65 weight percent of the present compositions, such as from 3to 40 weight percent or 5 to 35 weight percent, with weight percentbased on the total weight of the compositions.

Photoactive dyes, which provide reversible or permanent photoinducedcolor change effects, are also suitable for use in the compositionsdescribed herein. Suitable photoactive dyes are commercially availablefrom Spectra Group Limited, Inc., Millbury, Ohio.

Thixotropes, for example silica, are often used in an amount from 0.1 to5 weight percent, based on the total weight of the composition.

Retardants, such as stearic acid, likewise often are used in an amountfrom 0.1 to 5 weight percent, based on the total weight of thecomposition. Conventional adhesion promoters, if employed, are oftenpresent in amount from 0.1 to 15 weight percent, based on the totalweight of the composition. Suitable such adhesion promoters includephenolics, such as METHYLON phenolic resin available from OccidentalChemicals, and organosilanes, such as epoxy, mercapto or aminofunctional silanes, such as Silquest A-187 and Silquest A-1100 availablefrom Momentive Performance Materials. Masking agents, such as pinefragrance or other scents, which are useful in covering any low levelodor of the composition, are often present in an amount from 0.1 to 1weight percent, based on the total weight of the composition.

In certain embodiments, the compositions comprise a plasticizer, which,in at least some cases, may allow the composition to include polymerswhich have a higher T_(g) than would ordinarily be useful in anaerospace sealant. That is, use of a plasticizer may effectively reducethe T_(g) of the composition, and thus increase the low-temperatureflexibility of the cured composition beyond that which would be expectedon the basis of the T_(g) of the polymer alone. Plasticizers that areuseful in certain embodiments of the compositions of the presentinvention include, for example, phthalate esters, chlorinated paraffins,and hydrogenated terphenyls. The plasticizer or combination ofplasticizers often constitute 1 to 40 weight percent, such as 1 to 10weight percent of the composition. In certain embodiments, depending onthe nature and amount of the plasticizer(s) used in the composition,polymers of the invention which have T_(g) values up to −50° C., such asup to −55° C., can be used.

In certain embodiments, the compositions can further comprise one ormore organic solvents, such as isopropyl alcohol, in an amount rangingfrom, for example, 0 to 15 percent by weight on a basis of total weightof the composition, such as less than 15 weight percent and, in somecases, less than 10 weight percent. In certain embodiments, however, thecompositions of the present invention are substantially free or, in somecases, completely free, of any solvent, such as an organic solvent or anaqueous solvent, i.e., water. Stated differently, in certainembodiments, the compositions of the present invention are substantially100% solids.

As should be appreciated from the foregoing description, the presentinvention is also directed to compositions comprising: (a) athiol-terminated polythioether; and (b) a polyene comprising a polyvinylether and/or a polyallyl compound. These compositions comprise anessentially stoichiometric equivalent amount of thiol groups and enegroups. Moreover, these compositions may comprise one or more of theadditional optional components described earlier.

As should also be appreciated from the foregoing description, thepresent invention is also directed to compositions comprising: (a) athiol-terminated polythioether; (b) a polyene comprising a polyvinylether and/or a polyallyl compound; (c) a hydroxy-functional vinyl ether,and (d) a photoinitiator. Moreover, these compositions may comprise oneor more of the additional optional components described earlier.

In certain embodiments, a coating or sealant may include a small amountof reactive diluent such as hydroxy-functional vinyl ether or other lowviscosity compound having a terminal hydroxy group, such as a linearhydrocarbon having a terminal hydroxy group. In certain embodiments, theamount of reactive diluent in a composition may be from about 0 wt % toabout 3 wt %, from about 0.25 wt % to about 2 wt %, from about 0.5 wt %to about 1 wt %, and in certain embodiments, about 0.5 wt %.

In certain embodiments, compositions provided by the present disclosureinclude a hydroxy-functional vinyl ether. In certain embodiments, ahydroxy-functional vinyl ether has the structure of Formula (VI):

CH₂═CH—(CH₂)_(d)—OH  (VI)

wherein d is an integer from 0 to 10. In certain embodiments, d is aninteger from 1 to 4. Examples of suitable hydroxy-functional vinylethers include triethylene glycol monovinyl ether, 1,4-cyclohexanedimethylol monovinyl ether, 1-methyl-3-hydroxypropyl vinyl ether,4-hydroxybutyl vinyl ether, and a combination of any of the foregoing.In certain embodiments, the hydroxy-functional vinyl ether is4-hydroxybutyl vinyl ether.

In certain embodiments, compositions provided by the present disclosureinclude from about 60 wt % to 90 wt % of a thiol-terminatedpolythioether such as a combination of Permapol® polymers L1633 andL56086, from 70 wt % to 90 wt %, and in certain embodiments from 75 wt %to 85 wt % of a thiol-terminated polythioether prepolymer, where wt % isbased on the total solids weight of the composition.

In certain embodiments, compositions provided by the present disclosureinclude from about 1 wt % to about 5 wt % of divinyl ether such astriethylene glycol divinyl ether, from about 2 wt % to about 4 wt %, andin certain embodiments from about 2.5 wt % to about 3.5 wt % of adivinyl ether.

In certain embodiments, compositions provided by the present disclosureinclude from about 0.5 wt % to about 4 wt % of a polyfunctionalizingagent such as triallyl cyanurate, from about 0.5 wt % to about 3 wt %,and in certain embodiments, from about 0.5 wt % to about 2 wt % of apolyfunctionalizing agent.

In certain embodiments, compositions provided by the present disclosureinclude from about 0.05 wt % to about 2 wt % of a hydroxy-functionalvinyl ether such as 4-hydroxybutyl vinyl ether, from about 0.1 wt % toabout 1 wt %, and in certain embodiments, from about 0.2 wt % to about0.7 wt % of a hydroxy-functional vinyl ether.

In certain embodiments, the compositions of the present invention have aT_(g) when cured not higher than −55° C., such as not higher than −60°C., or, in some cases, not higher than −65° C.

As described above, the methods of the present invention compriseexposing the uncured sealant composition described above to actinicradiation to provide a cured sealant. The Examples herein describesuitable conditions for performing this method step. In some embodimentsof the present invention, the thiol-ene reaction, which forms the curedsealant, is effected by irradiating an uncured composition comprising:(a) a thiol-terminated polythioether (such as any of those describedabove); and (b) a polyene comprising a polyvinyl ether and/or apolyallyl compound as described above, with actinic radiation. As usedherein, “actinic radiation” encompasses electron beam (EB) radiation,ultraviolet (UV) radiation, and visible light. In many cases, thethiol-ene reaction is effected by irradiating the composition with UVlight and, in such cases, as mentioned above, the composition oftenfurther comprises a photoinitiator, among other optional ingredients.

Ultraviolet radiation from any suitable source which emits ultravioletlight having a wavelength ranging from, for example, 180 to 400nanometers, may be employed to initiate the thiol-ene reaction describedabove and thereby form the cured sealant. Suitable sources ofultraviolet light are generally known and include, for example, mercuryarcs, carbon arcs, low pressure mercury lamps, medium pressure mercurylamps, high pressure mercury lamps, swirl-flow plasma arcs andultraviolet light emitting diodes. Certain embodiments of thecompositions of the invention can exhibit an excellent degree of cure inair at relatively low energy exposure in ultraviolet light.

In fact, it has been discovered, surprisingly, that UV cure of thecompositions of the present invention to depths of up to 2 inches ormore can be achieved in some cases. This means that cured sealantshaving a thickness of 2 inches or more, and having desirable sealantproperties described herein, can be achieved by exposure of thecompositions described herein to actinic radiation, such as ultravioletradiation, in air at relatively low energy exposure.

As indicated, certain embodiments of the present invention are directedto compositions, such as sealant, coating, and/or electrical pottingcompositions. As used herein, the term “sealant composition” refers to acomposition that is capable of producing a film that has the ability toresist atmospheric conditions, such as moisture and temperature and atleast partially block the transmission of materials, such as water,fuel, and other liquid and gasses. In certain embodiments, the sealantcompositions of the present invention are useful, e.g., as aerospacesealants and linings for fuel tanks.

In certain embodiments, the sealants produced according to the methodsof the present invention are fuel-resistant. As used herein, the term“fuel resistant” means that a sealant has a percent volume swell of notgreater than 40%, in some cases not greater than 25%, in some cases notgreater than 20%, in yet other cases not more than 10%, after immersionfor one week at 140° F. (60° C.) and ambient pressure in jet referencefluid (JRF) Type I according to methods similar to those described inASTM D792 or AMS 3269, incorporated herein by reference. Jet referencefluid JRF Type I, as employed herein for determination of fuelresistance, has the following composition (see AMS 2629, issued Jul. 1,1989), § 3.1.1 et seq., available from SAE (Society of AutomotiveEngineers, Warrendale, Pa.) (that is incorporated herein by reference):herein by reference):

Toluene 28 ± 1% by volume Cyclohexane (technical) 34 ± 1% by volumeIsooctane 38 ± 1% by volume Tertiary dibutyl disulfide 1 ± 0.005% byvolume (doctor sweet)

In certain embodiments, sealants produced according to the presentinvention have an elongation of at least 100% and a tensile strength ofat least 250 psi when measured in accordance with the proceduredescribed in AMS 3279, § 3.3.17.1, test procedure AS5127/1, § 7.7.

In certain embodiments, sealants produced according to the presentinvention have a tear strength of at least 25 pounds per linear inch(pli) or more when measured according to ASTM D624 Die C.

As should be apparent from the foregoing description, the presentinvention is also directed to methods for sealing an aperture utilizinga composition of the present invention. These methods comprise (a)applying a composition of the present invention to a surface to seal theaperture; and (b) curing the composition by exposing the composition toactinic radiation. As will also be appreciated, the present invention isalso directed to aerospace vehicles comprising at least a sealant formedas described herein.

Illustrating the invention are the following examples, which, however,are not to be considered as limiting the invention to their details.Unless otherwise indicated, all parts and percentages in the followingexamples, as well as throughout the specification, are by weight.

EXAMPLES Example 1: Polythioether Polymer Synthesis

A resin was prepared in the manner described in Example 1 of U.S. Pat.No. 6,232,401. The polymer (theoretical functionality: 2.2) had amercaptan equivalent weight of 1640 and a viscosity of 70 poise.

Example 2: Polythioether Polymer Synthesis

Triallylcyanurate (TAC) (36.67 g, 0.15 mole) and dimercaptodioxaoctane(DMDO) (449.47 g, 2.47 moles) were charged in a 1-liter 4-neckround-bottom flask. The flask was equipped with a stirrer, gas-passingadapter and thermometer. Stirring was started. The flask was flushedwith dry nitrogen, a solution of potassium hydroxide (0.012 g;concentration: 50%) was added and the reaction mixture was heated to 76°C. A solution of radical initiator Vazo-67 (0.32 g) in diethylene glycoldivinyl ether (316.44 g, 2.00 moles) was introduced in the reactionmixture over a period of 2 hours during which a temperature of 66-76° C.was maintained. Following the completion of the addition of the divinylether, temperature of the reaction mixture increased to 84° C. Thereaction mixture was cooled to 74° C. and nine portions of Vazo-67(˜0.15 g each) were added at an interval of 1 hour while the temperaturewas maintained at 74-77° C. The reaction mixture was heated at 100° C.for 2 hours, cooled to 80° C., and evacuated at 68-80° C./5-7 mmHg for1.75 hr. The resulting polymer (theoretical functionality: 2.8) had amercaptan equivalent weight of 1566, and a viscosity of 140 poise.

Example 3: Polythioether Polymer Synthesis

A resin was prepared in a manner similar to that described in Example 16of U.S. Pat. No. 4,366,307, with the exception that trimethylolpropane(TMP) was used to replace HDT (1,5,13-trihydroxy-7-oxa-dithiatridecane)that was synthesized in Example 3 of U.S. Pat. No. 4,366,307. Theresulting polymer (theoretical functionality: 2.75) had a mercaptanequivalent weight of 1704, and a viscosity of 400 poise.

Example 4: Curing of Polymer Example 1 with DEG-DVE

The curing reaction was performed in a 100 g plastic container with lid.The polymer described in Example 1 (50.00 g, 0.03equivalent mole) anddiethylene glycol divinyl ether (DEG-DVE) (2.40 g, 0.03 equivalent mole)were added to the 100 g container. The container was placed in a highspeed mixer (DAC 600 FVZ) and mixed for 1 minute at 2300 rpm. Thecontainer was opened and Irgacure® 2022 (A Bis AcylPhosphinekt-Hydroxyketone photoinitiator from BASF Corporation, 0.54 g,1% by weight) was added, and the container was closed and placed in thespeed mixer again and mixed for 30 seconds at 2300 rpm. The polymer waspoured over a circular (5 inches in diameter) metal lid (pre-treatedwith Valspar Mold Release 225), and placed under UV light for 15seconds, after which time the polymer had completely cured. The curingwas achieved using a Super Six curing unit, available from FusionSystems Inc. The curing unit was equipped with a 300 W H-bulb, whichproduced UV wavelengths ranging from 200 nm to 450 nm. A total dosage of3.103 J/cm² UV energy, measured by a UV power puck, available from EIT,Inc of Sterling, Va., was applied to the polymer composition. Up to 2inches of cured polymer was obtained. The hardness of the polymer wasmeasured with a Durometer to be 20 Shore A. The polymer was cut intosix, ½ inch dog bones with a tensile strength gauge, and three of thespecimens were used to measure dry (no water or fuel immersion) tensilestrength and elongation, via Instron. The results (an average of thethree) are as follows: 250 psi (tensile strength), and 1011%(elongation). One of the ½ inch dog bones was cut in half and placed in20 mL vial with lid and placed in a 200° F. (93° C.) oven. The samplewas kept at 200° F. (93° C.) for 2 days, after which time the hardnesswas checked to be 10 Shore A. Tensile strength and elongation data wereobtained according to ASTM D 412 and hardness data was obtainedaccording to ASTM D 2240.

Example 5: Curing of a Blend of Polymer Example 1 and Polymer Example 2with DEG-DVE

The curing reaction was performed in a 300 g plastic container with lid.The polymer described in Example 1 (120.00 g, 0.07 equivalent mole), thepolymer described in Example 2 (30.00 g, 0.02 equivalent mole), anddiethylene glycol divinyl ether (DEG-DVE) (7.25 g, 0.09 equivalent mole)were added to the 300 g container. The container was placed in a speedmixer (DAC 600 FVZ) and mixed for 1 minute at 2300 rpm. The containerwas opened and Irgacure® 2022 (0.79 g, 0.5% by weight) was added, andthe container was closed and placed in the speed mixer again and mixedfor 30 seconds at 2300 rpm. The polymer was equally distributed among 3circular (5 inches in diameter) metal lids (pre-treated with ValsparMold Release 225), and placed under UV light for 15 seconds, after whichtime the polymer had completely cured. The curing was achieved using aSuper Six curing unit, available from Fusion Systems Inc. The curingunit was equipped with a 300 W H-bulb, which produced UV wavelengthsranging from 200 nm to 450 nm. A total dosage of 3.103 J/cm² UV energy,measured by a UV power puck, available from EIT, Inc of Sterling, Va.,was applied to the polymer composition. Up to 2 inches of cured polymerwas obtained. The hardness of the polymer was measured with a Durometerto be 22 Shore A. The polymer was cut into twenty-one, ½ inch dog boneswith a tensile strength gauge. Dry tensile strength and elongation weremeasured, for 3 of the specimens via Instron. The results (an average ofthe three) are as follows: 258 psi (tensile strength), and 625%(elongation). Three of the ½ inch dog bones were placed in a glass jar,with a lid, and covered with jet reference fuel (JRF Type I) and placedin a 140° F. (60° C.) water bath for 7 days. The results (an average ofthe three) are as follows: 287 psi (tensile strength) and 755%(elongation). Three more of the dog bones were placed in glass jar withlid, covered with tap water, and placed in a 95° F. (35° C.) oven. Thesamples were kept in the 95° F. (35° C.) oven for 41 days. The results(an average of the three) are as follows: 19 Shore A (hardness), 191 psi(tensile strength), and 713% (elongation). Three additional samples weretaken used for 3% salt water immersion test. The samples were placed inglass jar with lid, placed in a 140° F. (60° C.) oven for 4.5 days. Theresults (an average of the three) are as follows: 20 A (hardness), 224psi (tensile strength), and 765% (elongation). Tensile strength andelongation data were obtained according to ASTM D 412 and hardness datawas obtained according to ASTM D 2240.

Example 6: Curing of Blend of Example 1 and Example 2 with TEG-DVE

The curing reaction was performed in a 100 g plastic container with lid.The polymer described in Example 1 (40.80 g, 0.02 equivalent mole), thepolymer described in Example 2 (10.20 g, 0.01 equivalent mole), andtriethylene glycol divinyl ether (TEG-DVE) (3.15 g, 0.03 equivalentmole) were added to the 100 g container. The container was placed in aspeed mixer (DAC 600 FVZ) and mixed for 1 minute at 2300 rpm. Thecontainer was opened and Irgacure® 2022 (0.26 g, 0.5% by weight) wasadded, and the container was placed in the speed mixer again and mixedfor 30 seconds at 2300 rpm. The polymer was poured over a circular (5inches in diameter) metal lid (pre-treated with Valspar Mold Release225), and placed under UV light for 15 seconds, after which time thepolymer had completely cured. The curing was achieved using a Super Sixcuring unit, available from Fusion Systems Inc. The curing unit wasequipped with a 300 W H-bulb, which produced UV wavelengths ranging from200 nm to 450 nm. A total dosage of 3.103 J/cm² UV energy, measured by aUV power puck, available from EIT, Inc of Sterling, Va., was applied tothe polymer composition. Up to 2 inches of cured polymer was obtained.The hardness of the polymer was measured with a Durometer to be 22 ShoreA. The polymer was cut into six, ½ inch dog bones with a tensilestrength gauge. Dry tensile strength and elongation were measured forthree of the specimens via the Instron. The results (an average of thethree) are as follows: 182 psi (tensile strength) and 660% (elongation).Three of the ½ inch dog bones were placed in a glass jar, with a lid,and covered with jet reference fuel (JRF Type I) and placed in a 140° F.(60° C.) water bath for 7 days. The results (an average of the three)are as follows: 248 psi (tensile strength), 658% (elongation). Tensilestrength and elongation data were obtained according to ASTM D 412 andhardness data was obtained according to ASTM D 2240.

Example 7: Curing of Polymer Example 3 with DEG-DVE

The curing reaction was performed in a 100 g plastic container with lid.The polymer described in Example 3 (50.00 g, 0.03 equivalent mole) anddiethylene glycol divinyl ether (DEG-DVE) (2.32 g, 0.03 equivalent mole)were added to the 100 g container. The container was placed in a speedmixer (DAC 600 FVZ) and mixed for 1 minute at 2300 rpm. The containerwas opened and Irgacure® 2022 (0.52 g, 1% by weight) was added, and thecontainer was closed and placed in the speed mixer again and mixed for30 seconds at 2300 rpm. The polymer was poured over a circular (5 inchesin diameter) metal lid (pre-treated with Valspar Mold Release 225), andplaced under UV light for 15 seconds, after which time the polymer hadcompletely cured. The curing was achieved using a Super Six curing unit,available from Fusion Systems Inc. The curing unit was equipped with a300 W H-bulb, which produced UV wavelengths ranging from 200 nm to 450nm. A total dosage of 3.103 J/cm² UV energy, measured by a UV powerpuck, available from EIT, Inc of Sterling, Va., was applied to thepolymer composition. Up to ¼ inches of cured polymer was obtained. Thehardness of the polymer was measured with a Durometer to be 18 Shore A.The polymer was cut into six, ½ inch dog bones with tensile strengthgauge, and three of the specimens were used to measure dry (no water orfuel immersion) tensile strength and elongation, via the Instron. Theresults (an average of the three) are as follows: 81 psi (tensilestrength), and 166% (elongation). Tensile strength and elongation datawere obtained according to ASTM D 412 and hardness data was obtainedaccording to ASTM D 2240.

Example 8: Sealant Composition Using Polymer Example 1

A sealant composition was prepared by mixing the polymer described inExample 1 with diethylene glycol divinyl ether (DEG-DVE) and otheringredients described in Table 1.

TABLE 1 Component Weight, in grams Polymer Example 1 300.00 DEG-DVE14.46 3-Mercaptopropyltrimethoxysilane 1.59 Silica 31.47 Calciumcarbonate 9.45 Irgacure ® 2022 0.81

All ingredients described in Table 1 were intimately mixed. A portion ofthe sealant composition was poured into a 2″ diameter plastic cup andcured for 15 seconds using a Super Six curing unit, available fromFusion Systems Inc. The curing unit was equipped with a 300 W H-bulb,which produced UV wavelengths ranging from 200 nm to 450 nm. A totaldosage of 3.103 J/cm² UV energy, measured by a UV power puck, availablefrom EIT, Inc of Sterling, Va., was applied to the sealant composition.Up to 1.5 inches of cured sealant was obtained.

Another portion of the sealant composition was poured between twopolyethylene sheets, pressed into a ⅛″ thick sheet using a hydraulicpress, and cured using the same curing unit described previously. A ⅛″thick flat sheet of cured sealant was obtained for tensile strength,elongation, tear strength and hardness measurement. The data are shownin Table 4.

Example 9: Sealant Composition Using Polymer Examples 1 and 2

A sealant was prepared by mixing polymer described in Example 1 andExample 2 with triethylene glycol divinyl ether (TEG-DVE) and otheringredients described in Table 2.

TABLE 2 Component Weight, in grams Polymer in Example 1 240.00 Polymerin Example 2 60.00 TEG-DVE 18.60 3-Mercaptopropyltrimethoxysilane 1.59Silica 31.83 Calcium carbonate 9.54 Irgacure ® 2022 0.81

All ingredients described in Table 2 were intimately mixed. A portion ofthe sealant composition was poured into a 2″ diameter paper cup andcured for 15 seconds using a Super Six curing unit, available fromFusion Systems Inc. The curing unit was equipped with a 300 W H-bulb,which produced UV wavelengths ranging from 200 nm to 450 nm. A totaldosage of 3.103 J/cm² UV energy, measured by a UV power puck, availablefrom EIT, Inc of Sterling, Va., was applied to the sealant composition.Up to 1.5 inches of cured sealant was obtained.

Another portion of the sealant composition was poured between twopolyethylene sheets, pressed into a ⅛″ thick sheet using a hydraulicpress, and cured using the same curing unit described previously. A ⅛″thick flat sheet of cured sealant was obtained for tensile strength,elongation, tear strength and hardness measurement. The data are shownin Table 4.

Example 10: Sealant Composition Using Polymer Example 3

A sealant was prepared by mixing polymer described in Example 3 withdiethylene glycol divinyl ether (DEG-DVE) and other ingredientsdescribed in Table 3.

TABLE 3 Component Weight, in kilograms Polymer Example 3 150.00 DEG-DVE6.96 Fumed Silica 15.70 Calcium Carbonate 4.71 Irgacure ® 2022 0.24

All ingredients described in Table 3 were intimately mixed. A portion ofthe sealant composition was poured into a 2″ diameter paper cup andcured for 15 seconds using a Super Six curing unit, available fromFusion Systems Inc. The curing unit was equipped with a 300 W H-bulb,which produced UV wavelengths ranging from 200 nm to 450 nm. A totaldosage of 3.103 J/cm² UV energy, measured by a UV power puck, availablefrom EIT, Inc of Sterling, Va., was applied to the sealant composition.Up to ¼″ inches of cured sealant was obtained.

Another portion of the sealant composition was poured between twopolyethylene sheets, pressed into a ⅛″ thick sheet using a hydraulicpress, and cured using the same curing unit described previously. A ⅛″thick flat sheet of cured sealant was obtained for tensile strength,elongation, tear strength and hardness measurement. The data are shownin Table 3.

Example 11: Comparative Example

The curing reaction was performed in a 400 g plastic container with lid.The polymer described in Example 1 (162.00 g, 0.10 equivalent mole) andtrimethylolpropane triacrylate (10.00 g, 0.10 equivalent mole) wereadded to the 400 g. The container was placed in a speed mixer (DAC 600FVZ) and mixed for 1 minute at 2300 rpm. The container was opened andIrgacure® 2022 (1.72 g, 1% by weight) was added, and the container wasclosed and placed in the speed mixer again and mixed for 30 seconds at2300 rpm. The polymer composition was placed under UV light for 15seconds for curing. The curing was achieved by using a Super Six curingunit, available from Fusion Systems Inc. The curing unit was equippedwith a 300 W H-bulb, which produced UV wavelengths ranging from 200 nmto 450 nm. A total dosage of 3.103 J/cm² UV energy, measured by a UVpower puck, available from EIT, Inc of Sterling, Va., was applied to thepolymer composition. Under such a curing condition, the polymercomposition did not form a solid elastomer, rather it gelled. Nomeasurable hardness, tensile strength, and elongation were obtained.

TABLE 4 Sealant Tensile Tear Hardness, Composition Strength, psiElongation, % Strength, pli Shore A Example 8 367 738 44 35 Example 9348 720 56 40 Example 10 270 279 36 40 Example 11 N/A¹ N/A¹ N/A¹ N/A¹¹Not measurable because a solid elastomer was not formed.

Example 12: Synthesis of Sulfur-Containing Ethylenically UnsaturatedSilane

In a 1-liter 4-necked round bottom flask fitted with stirrer, nitrogeninlet, and thermal probe, TAC (121.00 g, 0.49 mole) andγ-mercaptopropyltrimethoxysilane (Silquest® 189, 95.25 g, 0.49 mole)were added at room temperature (25° C., 77° F.). Upon addition there wassmall exotherm to 40° C. (104° F.). The reaction was slowly heated to70° C. (158° F.). Once the temperature reached 70° C. (158° F.), Vazo-67(0.026 g, 0.012% by weight) was added and the reaction was monitored bymercaptan titration (mercaptan titration indicating a mercaptanequivalent of greater 50,000 marked the end of the reaction). At amercaptan equivalent of 6100, Vazo 67 (0.042 g, 0.019% by weight) wasadded and the reaction was allowed to stir at 70° C. (158° F.) whilebeing monitored. At mercaptan equivalent of 16,335, Vazo-67 (0.036 g,1.7%) was added. At mercaptan equivalent of 39,942 Vazo-67 (0.016 g,0.007%) was added. At a mercaptan equivalent of 61,425 the reaction wasconsidered complete and stopped.

Example 13: Curing Polythioether Polymer With DEG-DVE/Adduct Blend

The curing reaction was performed in a 300 g plastic container with lid.The polymer of Example 1 (120.00 g, 0.07 equivalent mole), DEG-DVE (4.28g, 0.05 equivalent mole), and the adduct described in Example 12 (4.03g, 0.02 equivalent mole) were added to a 300 g container. The containerwas place in a speed mixer (DAC 600 FVZ) and mixed for 30 seconds for2300 rpm. The container was opened and Irgacure® 2022 (0.64 g, 0.5% byweight) was added, and the container was placed in the speed mixer againand mixed for 1 minute at 2300 rpm. The polymer was poured over circular(5 inches in diameter) metal lid (pre-treated with Valspar Mold Release225), and placed under UV light for 15 seconds, after which time thepolymer appeared to have cured. The curing was achieved using a SuperSix curing unit, available from Fusion Systems Inc. The curing unit wasequipped with a 300 W H-bulb, which produced UV wavelengths ranging from200 nm to 450 nm. A total dosage of 3.103 J/cm² UV energy, measured by aUV power puck, available from EIT, Inc of Sterling, Va., was applied tothe polymer composition. Up to 2 inches of cured polymer was obtained.The polymer was left at ambient temperature for 4 days to ensure that ithad fully cured. The hardness of the polymer, measured by a Durometerwas 31 Shore A. The polymer was cut into seven, ½ inch dog bones with atensile strength gauge. Dry tensile strength and elongation weremeasured for three of the specimens. The results (an average of thethree) are as follows: 282 psi (tensile strength) and 421% (elongation).Two of the ½ inch dog bones were placed in a glass jar, with a lid, andcovered with jet reference fuel (JRF Type I) and placed in a 140° F.(60° C.) water bath for 7 days. The results (an average of the two) wereas follows: 141 psi (tensile strength), 78% (elongation). Two of the ½inch dog bones were placed in a glass jar, with lid, covered with tapwater and placed in a 200° F. (93° C.) oven for 2 days. The results (anaverage of two) were as follows: 36 Shore A (hardness), 134 psi (tensilestrength), and 50% (elongation). Tensile strength and elongation datawere obtained according to ASTM D 412 and hardness data was obtainedaccording to ASTM D 2240.

A portion of the polymer composition was spread onto a 3″×6″ AMS-C-27725coated aluminum panel and cured according the curing method describedpreviously. An approximately ⅛″ thick cured polymer film was obtained.The film was further cut into two one-inch strips and the strips werepulled back at 180 degree angles with hands. The percent of adhesion tothe substrate was recorded and the results were shown in Table 7.

Example 14: Curing Polythioether Polymer with DEG-DVE/Adduct Blend

The curing reaction was performed in a 300 g plastic container with lid.The polymer described in Example 1 (120.00 g, 0.073 equivalent mole),DEG-DVE (5.20 g, 0.066 equivalent mole), and the adduct described inExample 12 (1.60 g, 0.007 equivalent mole) were added to the 300 gcontainer. The container was placed in a speed mixer (DAC 600 FVZ) andmixed for 30 seconds for 2300 rpm. The container was opened andIrgacure® 2022 (0.63 g, 0.5% by weight) was added, and the container wasplaced in the speed mixer again and mixed for 1 minute at 2300 rpm. Thepolymer was poured over circular (5 inches in diameter) metal lid(pre-treated with Valspar Mold Release 225), and placed under UV lightfor 15 seconds, after which time the polymer appeared to have cured. Thecuring was achieved using a Super Six curing unit, available from FusionSystems Inc. The curing unit was equipped with a 300 W H-bulb, whichproduced UV wavelengths ranging from 200 nm to 450 nm. A total dosage of3.103 J/cm² UV energy, measured by a UV power puck, available from EIT,Inc of Sterling, Va., was applied to the polymer composition. Up to 2inches of cured polymer was obtained. The polymer was left at ambienttemperature for 4 days to insure that it had fully cured. The hardnessof the polymer, measured by a Durometer was 30 Shore A. The polymer wascut into seven, ½ inch dog bones with a tensile strength gauge. Drytensile and elongation were measured for three of the specimens. Theresults (an average of the three) were as follows: 251 psi (tensilestrength) and 559% (elongation). Two of the ½ inch dog bones were placedin a glass jar, with a lid, and covered with jet reference fuel (JRFType I) and placed in a 140° F. (60° C.) water bath for 7 days. Theresults (an average of the two) were as follows: 202 psi (tensilestrength), 351% (elongation). Two of the ½ inch dog bones were placed ina glass jar, with lid, covered with tap water and placed in a 200° F.(93° C.) oven for 2 days. The results (an average of two) were asfollows: 25 Shore A (hardness), 204 psi (tensile strength), and 274%(elongation). Tensile strength and elongation data were obtainedaccording to ASTM D 412 and hardness data was obtained according to ASTMD 2240.

A portion of the polymer composition was spread onto a 3″×6″ AMS-C-27725coated aluminum panel and cured according the method describedpreviously. An approximately ⅛″ thick cured polymer film was obtained.The film was further cut into two one-inch strips and the strips werepulled back at 180 degree angles with hands. The percent of adhesion tothe substrate was recorded and the results were shown in Table 7.

Example 15: Sealant Composition

A sealant composition was prepared by mixing polymer described inExample 1 and the adduct prepared according to Example 12 withtriethylene glycol divinyl ether (TEG-DVE) and other ingredientsdescribed in Table 5.

TABLE 5 Component Charge Weight, grams Polymer from Example 1 300.00TEG-DVE 12.84 Adduct from Example 12 4.02 Calcium carbonate 9.39Irgacure ® 2022 1.62

All ingredients described in Table 5 were intimately mixed. A portion ofthe sealant composition was poured into a 2″ diameter paper cup andcured for 15 seconds using a Super Six curing unit, available fromFusion Systems Inc. The curing unit was equipped with a 300 W H-bulb,which produced UV wavelengths ranging from 200 nm to 450 nm. A totaldosage of 3.103 J/cm² UV energy, measured by a UV power puck, availablefrom EIT, Inc of Sterling, Va., was applied to the sealant composition.Up to 1.5 inches of cured sealant was obtained.

A portion of the polymer composition was spread onto a 3″×6″ AMS-C-27725coated aluminum panel and cured according the method describedpreviously. An approximately ⅛″ thick cured polymer film was obtained.The film was further cut into two one-inch strips and the strips werepulled back at 180 degree angles with hands. The percent of adhesion tothe substrate was recorded and the results were shown in Table 7.

Example 16: Curing Polythioether Polymer without Adduct

The curing reaction was performed in a 100 g plastic container with lid.The polymer described in Example 1 (50.00 g, 0.03 equivalent mole) anddiethylene glycol divinyl ether (DEG-DVE) (2.0 g, 0.03 equivalent mole)were added to the 100 g container. The container was placed in a highspeed mixer (DAC 600 FVZ) and mixed for 1 minute at 2300 rpm. Thecontainer was opened and Irgacure® 2022 (0.54 g, 1% by weight) wasadded, and the container was closed and placed in the speed mixer againand mixed for 30 seconds at 2300 rpm. The polymer was poured over acircular (5 inches in diameter) metal lid (pre-treated with Valspar MoldRelease 225), and placed under UV light for 15 seconds, after which timethe polymer had completely cured. The curing was achieved using a SuperSix curing unit, available from Fusion Systems Inc. The curing unit wasequipped with a 300 W H-bulb, which produced UV wavelengths ranging from200 nm to 450 nm. A total dosage of 3.103 J/cm² UV energy, measured by aUV power puck, available from EIT, Inc of Sterling, Va., was applied tothe polymer composition. Up to 2 inches of cured polymer was obtained.The hardness of the polymer was measured with a Durometer to be 20 ShoreA. The polymer was cut into six, ½ inch dog bones with a tensilestrength gauge, and 3 of the specimens were used to measure dry (nowater or fuel immersion) tensile strength and elongation, via Instron.The results (an average of the three) are as follows: 250 psi (tensilestrength), and 1011% (elongation). One of the ½ inch dog bone was cut inhalf and placed in 20 mL vial with lid and placed in a 200° F. (93° C.)oven. The sample was kept at 200° F. (93° C.) for 2 days after whichtime the hardness was checked to be 10 Shore A.

A portion of the polymer composition was spread onto a 3″×6″ AMS-C-27725coated aluminum panel and cured according the method describedpreviously. An approximately ⅛″ thick cured polymer film was obtained.The film was further cut into two one-inch strips and the strips werepulled back at 180 degree angles with hands. The percent of adhesion tothe substrate was recorded and the results were shown in Table 7.

Example 17

A sealant was prepared by mixing polymer described in Example 1 andpolymer described in Example 2 with diethylene glycol divinyl ether(DEG-DVE) and other ingredients described in Table 6.

TABLE 6 Component Weight, grams Polymer Example 1 240.00 Polymer Example2 60.00 DEG-DVE 14.28 Silquest ® A-189¹ 0.77 Water 0.16 CalciumCarbonate 9.33 Irgacure ® 2022 1.62 ¹Silquest A-189 ismercaptopropyltrimethoxy silane, available from Momentive PerformanceMaterials, Inc.

All ingredients described in Table 6 were intimately mixed. A portion ofthe sealant composition was poured into a 2″ diameter paper cup andcured for 15 seconds using a Super Six curing unit, available fromFusion Systems Inc. The curing unit was equipped with a 300 W H-bulb,which produced UV wavelengths ranging from 200 nm to 450 nm. A totaldosage of 3.103 J/cm² UV energy, measured by a UV power puck, availablefrom EIT, Inc of Sterling, Va., was applied to the sealant composition.Up to 1.5 inches of cured sealant was obtained.

A portion of the polymer composition was spread onto a 3″×6″ AMS-C-27725coated aluminum panel and cured according the method describedpreviously. An approximately ⅛″ thick cured polymer film was obtained.The film was further cut into two one-inch strips and the strips werepulled back at 180 degree angles with hands. The percent of adhesion tothe substrate was recorded and the results were shown in Table 7.

TABLE 7 Adhesion of Various Polymer Compositions to AMS-C-27725 CoatedAluminum Composition Adhesion Example 13 100% Cohesive Example 14 100%Cohesive Example 15 >95% Cohesive Example 16 0% Cohesive Example 17 <50%Cohesive

Example 18: Sealant with Hydroxy-Functional Vinyl Ether

A sealant was made according to the formulation shown in Table 8.

TABLE 8 Sealant Formulation Chemical Name Wt (g) Permapol ® PolymerL1633* 69.33 Permapol ® Polymer L56086* 7.70 Calcium Carbonate 0.05Fumed Silica 1.54 Gasil ® IJ35 Micronized Silica Gel** 16.66 TriallylCyanurate (TAC) 1.10 Triethylene Glycol Divinyl Ether (TEGDVE) 3.294-Hydroxylbutyl vinyl Ether (HBVE) 0.49γ-Mercapto-propyltrimethoxysilane (Silquest ® A-189) 0.10 Irgacure ®819*** 0.02 Darocur ®1173*** 0.08 *Commercially available fromPRC-Desoto International, Inc. **Commercially available from PQCorporation. ***Commercially available from BASF.

A plastic cup was charged with Permapol® polymers L1633 and L56086,calcium carbonate, fume silica, and Gasil® U35. The cup was sealed andplaced in a high speed mixer for 90 seconds until all fillers werehomogeneously dispersed in the resin. To this, TAC, TEGDVE, HBVE,Silquest® A-189, Darocure® 1173, and Irgacure® 819 were added at 23° C.The full formulation was then mixed in high-speed mixer for 30 seconds.

Peel strength test panel was prepared and cleaned in accordance toAS5127 (6), and assembled in accordance to AS5127/1C (8). An opticallyclear strip with transparency in the range of 350 nm to 450 nm was usedas the reinforcement in place of conventional metal mesh screen orcotton duck cloth. The sample was cured by exposure to Phoseon FireFlyUV LED curing lamp with peak irradiance at 395 nm for 1 minute.

Tensile and elongation samples were prepared in accordance to AS5127/1C(7.7). The sealant was cured by Phoseon FireFly UV LED curing lamp withpeak irradiance at 395 nm for 1 minute.

The hardness sample was prepared in accordance to AS5127/1C (6.2).Sealant was cured by Phoseon FireFly UV LED curing lamp with peakirradiance at 395 nm for 1 minute.

The performance of the sealant prior to exposure is shown in Table 9.

TABLE 9 Performance of Example 18 Sealant Prior to Exposure PeelStrength on MIL-C-27725  35 pli Tensile Strength 550 psi Elongation 325%Hardness 49 Shore A

The performance of the sealant after exposure is shown in Tables 10, 11,and 12.

TABLE 10 Performance of Example 18 Sealant After Fuel Immersion 60°C./167 hour fuel immersion Peel Strength on MIL-C-27725  31 pli TensileStrength 463 psi Elongation 337% Hardness 45 Shore A

TABLE 11 Performance of Example 18 Sealant After Water Immersion 35°C./1000 hour water immersion Peel Strength on MIL-C-27725  35 pliTensile Strength 556 psi Elongation 365% Hardness 49 Shore A

TABLE 12 Performance of Example 18 Sealant After Air Exposure After 80°C./2000 hour air exposure Peel Strength on MIL-C-27725  19 PLI TensileStrength 552 Psi Elongation 197%

Whereas particular embodiments of this invention have been describedabove for purposes of illustration, it will be evident to those skilledin the art that numerous variations of the details of the presentinvention may be made without departing from the invention as defined inthe appended claims

What is claimed is:
 1. A composition comprising: (a) a thiol-terminatedsulfur-containing prepolymer; and (b) a polyene; and (c) a photoactivecolorant.
 2. The composition of claim 1, wherein: the thiol-terminatedsulfur-containing prepolymer comprises a thiol-terminated polythioetherprepolymer; and the polyene comprises a polyvinyl ether.
 3. Thecomposition of claim 1, wherein the photoactive colorant comprises aphotoactive dye.
 4. The composition of claim 1, wherein the photoactivecolorant comprises a photochromic pigment.
 5. The composition of claim1, wherein the photoactive colorant is capable of exhibiting areversible photoinduced color change effect.
 6. The composition of claim1, wherein the photoactive colorant is capable of exhibiting anirreversible photoinduced color change effect.
 7. The composition ofclaim 1, wherein the photoactive colorant is capable of exhibiting areversible photoinduced color change effect.
 8. The composition of claim1, wherein the colorant comprises carbazole dioxazine crude pigment,azo, monoazo, naphthol AS, salt type (flakes), benzimidazolone,isoindolinone, isoindoline and polycyclic phthalocyanine, quinacridone,perylene, perinone, diketopyrrolol pyrrole, thioindigo, anthraquinone,indanthrone, anthrapyrimidien, flavanthrone, pyranthrone, anthanthrone,dioxazine, triarylcarbonium, quinophthalone pigments, diketo pyrrolopyrrole red, or combinations of any of the foregoing.
 9. The compositionof claim 1, wherein the composition comprises from 1 wt % to 65 wt % ofthe photoactive colorant, wherein wt % is based on the total weight ofthe composition.
 10. The composition of claim 1, wherein thethiol-terminated polythioether comprises a structure having the formula:—R¹—[—S—(CH₂)₂—O—[—R²—O—]_(m)—(CH₂)₂—S—R¹—]_(n)— wherein, (1) each R′independently comprises C₂₋₁₀ linear alkylene, C₂₋₆ branched alkylene,C₆₋₈ cycloalkylene, C₆₋₁₀ alkylcycloalkylene,—[(—CH₂—)_(p)—X—]_(q)—(—CH₂)_(r)—, or —[(—CH₂—)_(p)—X—]_(q)—(—CH₂—)_(r)—in which at least one —CH₂— unit is substituted with a methyl group,wherein: (i) each X independently comprises O, S, and —NR⁶—, wherein R⁶is hydrogen or methyl; (ii) p is an integer from 2 to 6; (iii) q is aninteger from 0 to 5; and (iv) r is an integer from 2 to 10; (2) each R²independently comprises C₂₋₁₀ linear alkylene, C₂₋₆ branched alkylene,C₆₋₈ cycloalkylene, C₆₋₁₀ alkylcycloalkylene, or—[(—CH₂—)_(p)—X—]_(q)—(—CH₂—)_(r)—, wherein: (i) each X independentlycomprises O, S, and —NR⁶—, wherein R⁶ is hydrogen or methyl; (ii) p isan integer from 2 to 6; (iii) q is an integer from 0 to 5; and (iv) r isan integer from 2 to 10; (3) m is an integer from 0 to 10; and (4) n isan integer from 1 to
 60. 11. The composition of claim 1, wherein thepolyene comprises a polyvinyl ether of Formula (IV):—CH₂═CH—O—(—R⁵—O—)—CH═CH₂  (IV) wherein, m is an integer from 0 to 10;each R⁵ independently comprises C₂₋₆ n-alkylene, C₂₋₆ branched alkylene,C₆₋₈ cycloalkylene, C₆₋₁₀ alkylcycloalkylene, or—[(—CH₂)—)_(p)—O—]_(q)—(—CH₂—)_(r)—, wherein, p is an integer from 2 to6; q is an integer from 1 to 5; and r is an integer from 2 to
 10. 12.The composition of claim 1, wherein the polyene comprises a divinylether.
 13. The composition of claim 1, wherein the polyene comprisesdivinyl ether, ethylene glycol divinyl ether, butanedioldivinyl ether,hexanediol divinyl ether, diethylene glycol divinyl ether, andtetraethylene glycol divinyl ether, or a combination of any of theforegoing.
 14. The composition of claim 1, wherein the polyene comprisesa triallyl compound.
 15. The composition of claim 1, wherein the polyenecomprises triallyl cyanurate, triallyl isocyanurate, or a combinationthereof.
 16. The composition of claim 1, wherein the polyene does notcomprise triethyleneglycol divinyl ether or cyclohexanedimethanoldivinyl ether.
 17. The composition of claim 1, further comprising: (d) asulfur-containing ethylenically unsaturated silane adduct, wherein thesulfur-containing ethylenically unsaturated silane adduct comprises thereaction product of reactants comprising (i) a mercaptosilane, and (ii)a polyene.
 18. The composition of claim 17, wherein: (i) themercaptosilane has the structure of formula (V)HS—R—Si(R¹)_(m)(OR′)_(3-m)  (V) wherein, (i) R is a divalent organicgroup; (ii) R′ is hydrogen or an alkyl group; (iii) R¹ is hydrogen or analkyl group; and (iv) m is an integer from 0 to 2; and (ii) the polyene(ii) comprises a triene.
 19. The composition of claim 17, wherein theethylenically unsaturated silane adduct comprises at least one thiolgroup and at least one silane group.
 20. The composition of claim 1further comprising a photoinitiator.
 21. The composition of claim 1,wherein the composition is formulated as an aerospace sealant.
 22. Acured composition prepared from the composition of claim
 1. 23. Anaerospace vehicle comprising the cured composition of claim
 22. 24. Aseal cap comprising the cured composition of claim
 22. 25. A method ofusing the composition of claim 1, comprising: applying the compositionof claim 1 to a surface; and exposing the applied composition to actinicradiation.
 26. The method of claim 25, wherein exposing the appliedcomposition to actinic radiation causes a color change effect.
 27. Themethod of claim 25, wherein exposing the applied composition to actinicradiation cures the sealant.
 28. The method of claim 25, wherein theactinic radiation comprises electron beam radiation, ultravioletradiation, visible light, or a combination of any of the foregoing. 29.An unreacted composition comprising: (a) a thiol-terminatedpolythioether; (b) a polyene comprising a polyvinyl ether and apolyallyl compound; (c) a reactive diluent, wherein, the reactivediluent comprises a hydroxyl-functional vinyl ether having the structureof Formula (VI):CH₂═CH—O—(CH₂)_(d)—OH  (VI) wherein, d is an integer from 1 to 10; (d) afiller; (e) a photoinitiator; and (f) a photoactive colorant; whereinthe composition is curable with ultraviolet light, and wherein thecomposition, when cured, exhibits an elongation of at least 100% and atensile strength of at least 250 psi determined in accordance to theprocedure described in AMS 3279, § 3.3.17.1, test procedure AS5127/1, §7.7.
 30. A cured composition prepared by curing the composition of claim29.